Preservative formulations are a critical component of numerous consumer products, including cosmetic products like facial creams, face and body washes, or other products intended for application on the user's skin. Most of these products contain some amount of water, whether in the form of an oil-in-water and/or water-in-oil emulsion. The presence of an aqueous phase serves as a breeding ground for microbes, which over time cause the product to deteriorate and become unstable, a phenomenon typically referred to as microbial spoilage. Because microbes are abundantly present in the air and on users' skin, nearly any use of topical products is likely to introduce microbes, and if the product is not properly preserved, spoilage can occur within days of exposure to the microbes—thereby rendering the product unsafe and undesirable for use. Hence, the addition of some sort of preservative agent is imperative to prevent microbial spoilage and facilitate an acceptable shelf life for topical consumer products.
Preservative formulations have historically included synthetic or petroleum-derived additives that provide broad-spectrum protection against microbial growth at low concentrations and promote a long shelf-life. One major class of preservative traditionally used is commonly referred to as “parabens,” which includes methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid. Higher esters are even more active than the butyl esters, but because of their decreased solubility, their use as a preservative has been limited. Benzoic acid may be used as either an acid or a salt, such as sodium benzoate. Regardless of form, the use of parabens has been considered hazardous to human health, causing the development of significant market pressures for the production of parab en-free products.
An early response to the consumer demand for paraben-free topical consumer products was the widespread use of phenoxyethanol as a preservative that was originally considered to be a safer “paraben alternative.” Although the use of phenoxyethanol as a preservative is globally permitted in skin and cosmetic products in amounts of up to 1% by weight, conflicting research has brought its safety into question.
Problematically, phenoxyethanol tends to accumulate in live cells where it becomes toxic and deleterious to cellular function, and it is often included in cosmetics at levels in excess of regulations. Further, because phenoxyethanol is petroleum based, and ethoxylated, it is believed that exposure to phenoxyethanol is linked to various negative health reactions ranging from eczema to severe, life-threatening allergic reactions. Despite these concerns, the use of phenoxyethanol as a preservative remains quite prevalent. For example, phenoxyethanol is often utilized to supplement or boost other preservative ingredients, such as weak acids like salicylic, benzoic, levulinic, etc., thereby reducing the overall weight percent of the preservative formulation in the cosmetic product—often to 1% or less.
Other commonly used preservatives have received similar scrutiny and engender a reluctance on the part of consumers to use products that contain them. One such category of preservatives includes formaldehyde-releasing compounds like imidazolidinyl urea, diazolidinyl urea, 1,3-bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione (also known as DMDM hydantoin), and quaternium-15. Many topical consumer products rely on either imidazolidinyl urea or diazolidinyl urea, alone or in combination with other preservatives such as parabens, to provide the requisite broad-spectrum protection against microbial growth. However, as with parabens, there is an increasing reluctance on the part of consumers to use products that contain formaldehyde-releasing preservatives. Exposure to formaldehyde is known to cause eye, nose, and throat irritation, and at sufficiently high levels can lead to skin rashes, shortness of breath, wheezing, changes in lung functions, and even cancer of at least the nose and throat. Children, the elderly, and people with preexisting breathing or lung conditions are especially vulnerable to formaldehyde's adverse health effects.
The use of harsh and frequently harmful chemicals like parabens and formaldehyde-releasing preservatives has been previously tolerated because of their effectiveness as effective, low-dose preservatives throughout the product's shelf life and, significantly, because of the prohibitive cost and difficulty of providing an effective “organic” or “natural” alternative. However, there is a strong consumer-led trend away from topical consumer products that include traditional hazardous or irritating preservatives and toward products that are deemed “organic” or “natural.” In line with the philosophy of such products, consumers also expect them to be paraben free, phthalate free, sulfate free, silicone free, synthetic fragrance free, alcohol free, phenoxyethanol free, or otherwise non-toxic.
In response to the outstanding need in the industry for products that meet certain thresholds of “natural” and “organic” ingredients, coupled with the lack of official standards for what qualifies as “natural” and “organic,” preservative formulation has become a cottage industry with consumers gravitating towards products containing natural extracts, botanicals, or other ingredients derived from natural sources, while avoiding those products having ingredients that are either known to cause or suspected of causing adverse health reactions. Unfortunately, this ad hoc approach and decentralization of acquired knowledge and experience of generating effective preservative formulations has led to a host of ineffective solutions that typically result in diminished shelf-life and usability of associated topical consumer products.
Various third-party certifications have been established in an attempt to bring consistency and reliability to the use of natural and organic preservatives in topical consumer products. For example, ECOCERT® is an organic certification organization based in Europe that conducts inspections in over 80 countries, making it one of the largest organic certification organizations in the world. ECOCERT® primarily certifies food and food products but also certifies cosmetics, detergents, perfumes, and textiles and is a leading certifier of fair-trade food, cosmetics, and textiles.
Another example is the Cosmetic Organic Standard (COSMOS), a Europe-wide private standard that was developed by five charter members: BDIH (Germany), Cosmebio (France), Ecocert Greenlife SAS (France), ICEA (Italy), and Soil Association (Great Britain). They were all combined under an AISBL (international non-profit organization based in Brussels), the purpose of which was to set out minimum common requirements, harmonize organic and natural cosmetic certification rules, and lobby institutions in the sector's interests. COSMOS makes use of the principles in the ECOCERT® standard: to promote the use of ingredients from organic farming, use production and manufacturing processes that are environmentally sound and safe for human health, and include and expand the concept of “green chemicals.”
The National Organic Program (NOP), a federal regulatory framework in the United States governing organic food, is yet another certification. The core mission of the NOP is to protect the integrity of the United States Department of Agriculture (USDA) organic seal. The seal is used for products adhering to USDA standards that contain at least 95% organic ingredients.
Despite the certification systems pressuring the market to identify preservative systems as such and despite the upwelling demand and need for all-natural preservative systems, existing efforts have fallen short in identifying natural preservative formulations that omit harsh preservatives while also maintaining effective broad-spectrum protection. For instance, it is known that essential oils alone are insufficient as a broad-spectrum preservative and that there are few “green” alternatives to harsh synthetic/petroleum-based preservatives. Current efforts discourage the omission of phenoxyethanol from a preservative formulation because of the cost and volume associated with consequently increasing the remaining preservatives, e.g. an increase of about 500% by weight and cost.
Certain preservative formulations supplement natural ingredients, such as antimicrobial peptides secreted by Lactobacillus sp., with synthetic and/or harsh preservatives. For example, U.S. Pat. No. 9,700,507 utilizes phenoxyethanol in formulas having a pH less than 6 in combination with Lactobacillus-derived antimicrobial peptides. Of note, however, phenoxyethanol is necessarily provided in the preservative formulation in addition to the Lactobacillus-derived antimicrobial peptides to achieve the desired preservation characteristics.
The use of natural preservatives is also discussed in non-patent literature forums like “Bacteria Hack: Pre- and Probiotics in Skincare.” Therein, Lactobacillus fermentation products, including antimicrobial peptides, are used to control the growth of microorganisms with a goal of maintaining a healthy balance of microbes on the user's skin while at the same time preserving compositions from microbial spoilage. It is discussed that antimicrobial peptides must be combined with the use of levulinic acid and anisic acid, among other ingredients, at a pH of 5.5 so as to maintain Staphylococcus epidermidis on a user's skin—thereby significantly narrowing the applicability and range of perseveration conditions.
Accordingly, existing efforts to create all-natural preservative formulations for cosmetics illustrate the difficulty of omitting harsh synthetic preservatives such as phenoxyethanol without compromising the effectiveness of the preservative formulation and are otherwise limited to the combination of antimicrobial peptides of Lactobacillus, levulinic acid, and anisic acid at a pH of 5.5 to preserve S. epidermidis colonization.
There remains a need for a broad-spectrum and natural preservative system for cosmetics and other topical consumer products that avoids the use of harsh preservatives. Further, because of the need for safe and effective preservative formulations for consumer products and because of the challenges of existing natural preservative formulations to provide broad-spectrum protection in the absence of synthetic and undesirable ingredients, such as phenoxyethanol, there is a need for an improved preservative formulation utilizing only natural, green, and/or plant-based ingredients that provides effective broad-spectrum antimicrobial preservation. There is further a need for a preservative formulation that omits harsh preservatives such as parabens, formaldehyde-donors, and phenoxyethanol without compromising effective preservation.
An ideal preservative system kills and/or prevents the growth of a wide range of Gram-positive and Gram-negative bacteria, yeasts, and molds without fostering resistance to the preservative. It should be rapid acting and chemically and biologically stable throughout the manufacturing and packaging processes, as well as during storage prior to and after sale to a consumer—all while still providing in-container sanitization against repeated microbial challenge. Ideally, the system should be colorless, odorless and remain so throughout the expected shelf life of the product.
When considering commercialization, the total cost of a preservative system, its compatibility with other ingredients, and regulatory restrictions of its component parts can further complicate the selection and use of preservatives. Further, the particular choice and amount of preservative to be used within an ideal preservative system must be balanced to retain efficacy in killing and/or inhibiting the growth of microbes while at the same time not causing any deleterious health effects to the user, such as skin irritation and/or allergic sensitization. To this end, the preservative system should be natural and should comprise antimicrobial compounds in such combinations and proportions as to provide efficacious preservation while avoiding skin irritation.
Unfortunately, with all of the above-mentioned requirements and prohibitions, no single preservative agent or system has yet been identified that can accomplish these goals.
Hence, it is an object of the present disclosure to provide a natural preservative system having ingredients that are internationally acceptable (e.g., ECOCERT®-approved). Another object of the present disclosure is to provide a preservative system that can be successfully and efficaciously incorporated into an ECOCERT®-approved, natural, and organic product without negatively affecting the product's ECOCERT®, natural, and/or organic third-party certification. Yet another object is to provide an efficacious preservative system free of parabens, formaldehyde, phenoxyethanol and, in general, any petroleum-derived preservatives and ingredients. The preservative system is ideally natural and/or plant-based as opposed to synthetic.